fix: prevent icon selection on mobile when editing dashboard

Add user-select: none and -webkit-touch-callout: none to app icon
to prevent the browser from selecting the image when long-pressing,
which interferes with drag-to-move in edit mode on mobile devices.

Closes #2970

packages/widgets/src/app/app.module.css

@@ -6,6 +6,8 @@
   object-fit: contain;
   scale: 0.8;
   transition: scale 0.2s ease-in-out;
+  user-select: none;
+  -webkit-touch-callout: none;
 }
 
 .appWithUrl:hover > .appIcon {